Biochemistry 2004, 43, 13129-13136
13129
Effects of Virion and Salt Concentrations on the Raman Signatures of Filamentous Phages fd, Pf1, Pf3, and PH75† Stacy A. Overman,‡ David M. Kristensen,‡,§ Priya Bondre,‡ Barbara Hewitt,‡ and George J. Thomas, Jr.*,‡ DiVision of Cell Biology and Biophysics, School of Biological Sciences, UniVersity of MissourisKansas City, 5100 Rockhill Road, Kansas City, Missouri 64110 ReceiVed July 14, 2004
ABSTRACT: Filamentous phages consist of a single-stranded DNA genome encapsidated by several thousand copies of a small R-helical coat protein subunit plus several copies of four minor proteins at the filament ends. The filamentous phages are important as cloning vectors, vehicles for peptide display, and substrates for macromolecular alignment. Effective use of a filamentous phage in such applications requires an understanding of experimental factors that may influence the propensity of viral filaments to laterally aggregate in solution. Because the Raman spectrum of a filamentous phage is strongly dependent on the relative orientation of the virion with respect to the polarization direction of the electromagnetic radiation employed to excite the spectrum, we have applied Raman spectroscopy to investigate lateral aggregation of phages fd, Pf1, Pf3, and PH75 in solution. The results show that lateral aggregation of the virions and anisotropic orientation of the aggregates are both disfavored by high concentrations of salt (>200 mM NaCl) in solutions containing a relatively low virion concentration (
